1. Field of the Invention
The present invention relates to vertically mountable semiconductor devices and devices which orient semiconductor devices perpendicularly relative to a carrier substrate. In particular, this invention relates to vertical surface mount package assemblies and alignment devices for biasing leads of the semiconductor device against terminals on a carrier substrate to establish and maintain electrical communication therebetween. The present invention also relates to vertical surface mount packages with low impedance and to user-upgradable, vertical surface mount package assemblies.
2. State of the Art
Vertical surface mount packages are known in the art. When compared with traditional, horizontally mountable semiconductor packages and horizontally oriented multi-chip packages, many vertical surface mount packages have a superior ability to transfer heat. Vertical surface mount packages also consume less area on a carrier substrate than a horizontally mounted package of the same size. Thus, many skilled individuals in the semiconductor industry are finding vertical surface mount packages more desirable than their traditional, horizontally mountable counterparts.
Exemplary vertical surface mount packages are disclosed in the following U.S. Pat. No. Re. 34,794 (the xe2x80x9c""794 patentxe2x80x9d), issued to Warren M. Farnworth on Nov. 22, 1994; U.S. Pat. No. 5,444,304 (the xe2x80x9c""304 patentxe2x80x9d), issued to Kouija Hara and Jun Tanabe on Aug. 22, 1995; U.S. Pat. No. 5,450,289, issued to Yooung D. Kweon and Min C. An on Sep. 12, 1995; U.S. Pat. No. 5,451,815, issued to Norio Taniguchi et al. on Sep. 19, 1995; U.S. Pat. No. 5,592,019, issued to Tetsuya Ueda et al. on Jan. 7, 1997; and U.S. Pat. No. 5,635,760, issued to Toru Ishikawa on Jun. 3, 1997.
The ""794 patent discloses a vertical surface mount package having a gull-wing, zig-zag, in-line lead configuration and a mechanism for mounting the package to a printed circuit board (PCB) or other carrier substrate. The force with which the package mounts to the carrier substrate establishes a tight interference contact between the package""s leads and their corresponding terminals on the carrier substrate.
The ""304 patent describes a vertical surface mount package which has integrally formed fins radiating therefrom. The fins of that device facilitate the dissipation of heat away from the device. The semiconductor device is electrically connected to the package""s leads by wire bonding. The leads of that vertical surface mount package, which extend therefrom in an in-line configuration, are mountable to the terminals of a carrier substrate by soldering.
However, many of the vertical surface mount packages in the prior art are somewhat undesirable from the standpoint that they permanently attach to a carrier substrate. Thus, those vertical surface mount packages are not readily user-upgradable. Moreover, many prior art vertical surface mount packages include relatively long leads, which tend to increase the impedance of the leads and reduce the overall speed of systems of which they are a part. Similarly, the wire bonding typically used in many vertical surface mount packages increases the impedance and reduces the overall speed of such devices. As the speed of operation of semiconductor devices increases, more heat is generated by the semiconductor device, requiring greater heat transfer. Similarly, as the speed of operation of semiconductor devices increases, it is important to decrease the length of the leads regarding circuitry connecting the semiconductor device to other components and thereby decrease the impedance of the leads to increase the responsiveness of the semiconductor device.
Vertical surface mount package sockets are also known in the art. Vertical surface mount package sockets support one or more vertical surface mount packages relative to a carrier substrate. Exemplary devices are disclosed in U.S. Pat. No. 5,619,067 (the xe2x80x9c""067 patentxe2x80x9d), which issued to Goh J. Sua and Chan M. Yu on Apr. 8, 1997, and U.S. Pat. No. 5,644,161 (the xe2x80x9c""161 patentxe2x80x9d), which issued to Carmen D. Burns on Jul. 1, 1997. The ""161 patent does not describe the platform shown therein in any detail.
The ""067 patent discloses a mechanism for vertically mounting a plurality of vertical surface mount packages onto a carrier substrate. A plurality of vertical surface mount packages is installed upside-down within a cover and against one another in a side-by-side arrangement. The cover is then inverted and attached to the carrier substrate. Clips on each side of the cover insert through and engage an edge of holes formed through the carrier substrate. The downward force of the cover on the vertical surface mount packages forces the leads against the corresponding contacts on the carrier substrate, creating electrical contact therebetween.
The cover of the ""067 patent is somewhat undesirable for several reasons. First, the vertical surface mount packages illustrated by that patent have conventional, long, bent leads. Such long leads tend to increase the impedance of such vertical surface mount packages. Second, the cover, as described, includes no mechanism for aligning the devices so that the corresponding leads and carrier substrate contacts match up to each other. The only alignment mechanism described by the ""067 patent is the two clips on the cover and the corresponding crude holes formed through the carrier substrate. Further, in order to effectively position the vertical surface mount packages and maintain adequate electrical contact between the vertical surface mount packages and the carrier substrate, the cover device of the ""067 patent must be filled to capacity with vertical surface mount packages. The illustrated clip-hole attachment mechanism also seems inadequate for establishing and maintaining an adequate interference contact between the vertical surface mount package leads and the carrier substrate contacts.
What is needed is a low impedance, vertical surface mount package which is readily removable from and reinstallable upon a carrier substrate. A vertical surface mount package alignment and attachment device which transfers heat away from the vertical surface mount package and establishes and maintains adequate electrical connections between a vertical surface mount package and a carrier substrate is also needed.
The vertically mountable semiconductor device assembly of the present invention includes very short stub contacts, which impart it with low impedance. The assembly of the present invention includes an alignment device, which exerts consistent downward force upon all of the vertically mountable semiconductor devices disposed therein to establish and maintain an electrical connection between the vertically mountable semiconductor device(s) and the carrier substrate. Vertically mountable semiconductor devices are readily removable from and reinstallable in the alignment device, making the device user-upgradable.
An embodiment of the system of the present invention includes a vertically mountable semiconductor device and an alignment device which attaches the vertically mountable semiconductor device to a carrier substrate. The alignment device of the present invention includes one or more receptacles formed therethrough, each of which receives and aligns at least one vertically mountable semiconductor device. The alignment device also includes a mechanism, which is referred to as a contact element, for biasing the vertically mountable semiconductor device(s) disposed within the receptacle(s) against the carrier substrate. A preferred contact element is a cover which exerts constant force on the vertically mountable semiconductor device to establish and maintain a connection with a carrier substrate. A preferred engagement mechanism releasably engages the vertically mountable semiconductor device(s) that has been inserted into the alignment device receptacle(s).
In use, the alignment device is mounted to a carrier substrate, one or more vertically mountable semiconductor devices are inserted into the receptacle(s) thereof, and the contact element engages the vertically mountable semiconductor device(s), exerting downward force thereon to establish and maintain an electrical connection between stub contacts on the vertically mountable semiconductor device(s) and corresponding terminals on the carrier substrate. Disengagement of the contact element facilitates the ready removal of the vertically mountable semiconductor device(s) from the alignment device. Consequently, each vertically mountable semiconductor device is readily removable from the receptacle and may also be readily replaced therein.
A vertically mountable semiconductor device which may be used in the system of the present invention has a plurality of short stub contacts extending therefrom. Preferably, the lead length is less than about one millimeter (mm). More preferably, the lead length is less than about one-half (xc2xd) mm. Shorter lead lengths of about 10 mils or less are even more preferred due to the decrease in impedance as lead length decreases. Thus, it is a consequent advantage that vertically mountable semiconductor devices which are useful in the system of the present invention have reduced impedance.
The present invention also includes a method for fabricating the vertically mountable semiconductor device and a method for modifying existing vertical surface mount packages to manufacture the vertically mountable semiconductor device of the present invention. A computer which includes the vertically mountable semiconductor device of the present invention is also within the scope of the invention.
Other advantages of the present invention will become apparent through a consideration of the appended drawings and the ensuing description.